Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.45	10.487%	$185.0105	$185.01	$185.00	$185.00
Purchase #2	$81.65	9.144%	$89.1161	$89.12	$89.10	$89.10
Purchase #3	$201.83	12.725%	$227.5129	$227.51	$227.50	$227.50
Purchase #4	$82.77	13.326%	$93.7999	$93.80	$93.80	$93.80
Purchase #5	$103.63	12.599%	$116.6863	$116.69	$116.70	$116.70
Purchase #6	$243.77	3.115%	$251.3634	$251.36	$251.35	$251.40
Purchase #7	$68.30	7.504%	$73.4252	$73.43	$73.45	$73.40
7 purchase totals =	$949.40		$1,036.9143	$1,036.92	$1,036.90	$1,036.90